A device for restoring competence to venous valves is known from International Patent Application No. WO 97/40755 (inventor ZUKOWSKI), published on 6th Nov., 1997, having the title Device for restoring Competence to Venous Valves, which is the closest prior art.
ZUKOWSKI's device is based on the discovery that an external force applied onto a vein, at the level of the coapting surfaces of an incompetent, slackened valve of such vein, flattens the vein with the aim to extend the cusps of the valve laterally, taking up their slackening and bringing them into apposition, restoring the competence of the vein.
So ZUKOWSKI's device features a support for applying a compressive, corrective force to an incompetent vein.
ZUKOWSKI discloses a support having a pair of opposite compression membranes which are identical, and generally rectangular. The membranes may have an elliptic or arcuate configuration, or may be flat with curved ends; they are joined together by an integrally formed, intermediate hinge portion which, when the support has been positioned about a valve, generally extends axially with respect to the vein and is placed to be adjacent to one of the commissures where the cusps of the valve attached to opposite walls of the vein meet; the width of the hinge determines the compressive force applied by the support to the valve. The device is implanted by suturing the free edges of the two rectangular members. The sutures perform the same function as the hinge, and they can regulate the compressive force of the device on the venous walls by their degree of tightening.
Problems are associated with ZUKOWSKI's device.
ZUKOWSKI's device has two compression membranes which are continuous surfaces. Owing to such continuity, to implant it, it is necessary to completely clear the posterior wall of the vein from surrounding tissues, and from all eventual collateral veins. Moreover, for the same reason it is not suitable for curing an incompetent valve located at the confluence of another vein owing to the asymmetry and anatomical variability of the confluence itself.
Moreover, the compression from outside envisaged with ZUKOWSKI's device, actually does not ensure a contemporaneous increase of the intercommissural diameter per se. It is a disadvantage of ZUKOWSKI's device that its compressive action actually is not reliable as regards its corrective action.
In fact, it is not sure that applying antero-posterior compressive forces though reducing the antero-posterior diameter of the vein, forcedly determines an enlargement of the latero-lateral intercommissural diameter of the vein valve, because, really, in vivo: depending on the normally arising contraction of the muscular component of the venous wall during the surgical dissection of the vein from the surrounding tissues; depending on blood pressure inside the vein, and, depending on hormone-, or drug-induced contraction of the muscular component of the venous wall, the vein is not in its final condition, as really turns out to be hypothesised in the spirit of ZUKOWSKI's device, so that a calibration thereof is difficult and probably incorrect.
Moreover, the venous spasm directly consequent to surgical manipulation reduces the diameter of the blood-vessel circumferentially, so that one does not have the best apposition of the two valve cusps and therefore it is not possible to check the valve competence intraoperatively, i.e. during an operation.